This invention relates to welding jigs and finds a particular application in the welding of strip material to form cellular grids for supporting or locating nuclear reactor fuel elements.
In known welding jigs for cellular grids used in nuclear reactor fuel element assemblies a base plate is jig drilled and a peg for each cell of the grid structure is pressfitted into the plate, adhesive being used in addition to ensure a firm fit. The strip material is formed to define cells and is located by pegs whilst being welded. To achieve a satisfactory grid the jig must be made to an extremely fine degree of accuracy calling for very close tolerances on the positions of the drillings for the pins and to produce a jig of such accuracy is expensive. Distortion can also occur when forcing a partly constructed grid on to the jig for welding with the result that the accuracy of the completed grid is impaired. Furthermore, it has been found very difficult to clean between the pegs during maintenance of the grid.